1. Field of the Invention
The present invention relates to a rotor for a dynamo-electric machine, the rotor being equipped with magnets provided between adjacent triangular magnetic poles to reduce the leakage of magnetic flux between the triangular magnetic poles.
2. Description of Related Art
FIG. 12 is a sectional side elevation of a conventional vehicular AC generator; and FIG. 13 is a perspective view of a rotor shown in FIG. 12. The AC generator is equipped with: a case 3 comprised of a front bracket 1 and a rear bracket 2 made of aluminum; a shaft 6 which is provided in the case 3 and which has a pulley 4 fixed at one end thereof; a Randell-type rotor 7 secured to the shaft 6; fans 5 secured to both side surfaces of the rotor 7; a stator 8 secured to the inner wall surface of the case 3; a slip ring 9 which is secured to the other end of the shaft 6 and which supplies current to the rotor 7; a pair of brushes 10 in sliding contact with the slip ring 9; a brush holder 11 which holds the brushes 10; a rectifier 12 which is electrically connected to the stator 8 to rectify alternating current generated in the stator 8 to direct current; a heat sink 17 fitted onto the brush holder 11; and a regulator 18 which is bonded to the heat sink 17 to adjust the magnitude of the AC voltage generated in the stator 8.
The rotor 7 is constituted by a rotor coil 13 through which current flows to generate magnetic flux, and a field core assembly 14 which is provided such that it covers the rotor coil 13 and in which magnetic poles are formed by the magnetic flux. The field core assembly 14 is composed of a pair of first field core member 21 and second field core member 22 which are alternately meshed. The first field core member 21 and the second field core member 22 are made of iron; the first field core member 21 has triangular magnetic poles 23, and the second field core member 22 has triangular magnetic poles 24. A hexahedral magnet 19 which has been magnetized in a direction so as to reduce the leakage of the magnetic flux between triangular magnetic poles 23 and 24 is secured at each pair of adjacent triangular magnetic poles 23 and 24.
The stator 8 is provided with a stator core 15, and a stator coil 16 which is composed of a conductor wound around the stator core 15 and in which alternating current is generated as the magnetic flux from the rotor coil 13 changes as the rotor 7 rotates.
In the vehicular AC generator configured as set forth above, current is supplied from a battery, not shown, to the rotor coil 13 via the brushes 10 and the slip ring 9 so as to generate magnetic flux; the triangular magnetic poles 23 of the first field core member 21 are magnetized to the N pole, while the triangular magnetic poles 24 of the second field core 22 are magnetized to the S pole. The pulley 4 is driven by an engine and the rotor 7 is rotated through the shaft 6, so that a rotary magnetic field is supplied to the stator coil 16, thus generating an electromotive force in the stator coil 16. This AC electromotive force is rectified into direct current through the rectifier 12 and the magnitude thereof is adjusted by the regulator 18 before it is supplied to the battery.
In the conventional vehicular AC generator, when the AC voltage is generated in the stator coil 16 as the rotor 7 rotates, a constant magnetic repulsion is generated between the outer peripheral surface of the rotor 7 and the inner peripheral surface of the stator 8; hence, vibration is apt to take place in the directions indicated by arrows A to the triangular magnetic poles 23 and 24 as shown in FIG. 14. Thus, there has been a problem in that a load applied to the triangular magnetic poles 23 and 24 causes the magnets 19, which have been secured to the triangular magnetic poles, to also be subjected to a load. This causes the magnet 19 to be distorted, and perhaps damaged.